The structure and function of the membrane-bound system of cellular respiration will be investigated in mammalian heart muscle mitochondria and the cytoplasmic membrane of Micrococcus denitrificans. Effort will be concentrated on the reactions of the intermediary electron carrier cytochrome c in the respiratory chain system of beef heart mitochondria. The kinetic properties of the reaction of soluble pure cytochrome c from a number of different species and of chemical derivatives of these will be investigated. Antibodies elicited to specific sites on the cytochrome c molecule will be employed to test the mechanism of reaction and o map reaction sites on the surface of the molecule. In addition, experiments with purified antibodies will examine the localization and mode of binding of the cytochrome c on the mitochondrial membrane. Attempts will be made to dissect relatively intact cytoplasmic membranes of Micrococcus denitrificans into large functional segments. The sytoplasmic membrane of these aerobic bacteria bears a respiratory chain system similar to that of mammalian mitochondria, and the composition of this membrane complex can be varied by changing growth conditions. The composition and function of the fragments obtained will furnish evidence on the distribution of lipids and proteins along the membrane, on the universal requirements for a functional respiratory chain system as well as specific requirements of the different segments of the chain. The proposed experiments should increase our understanding of two important aspects of cellular function: 1) the nature of the respiratory chain, which includes most of the energy-yielding reactions and 2) the structure and function of a multicomponent membrane-bound enzyme system.